Effect of interfacial reaction rate on the morphogenesis of nanostructured coatings in a simulated electrodeposition process

Brownian dynamics simulations (BDSs) are performed to investigate the influence of interfacial electrochemical reaction rate on the evolution of coating morphology on circular fibres. The boundary condition for the fluid phase concentration, representing the balance between the rates of interfacial reaction and transport of ions by bulk diffusion, is incorporated into the BDS by using a reaction probability, P_s. Different modes of growth, ranging from diffusion limited () to reaction controlled , are studied. It is found that, consistent with experimental observations, two distinct morphological regimes exist, with a dense and uniform structure for (reaction limited deposition (RLD)) and an open and porous one as (diffusion limited deposition (DLD)). An analysis of the fractal dimension indicates that this morphological transition occurs at P_s≈0.3. Long-time power-law scalings for the evolution of thickness and roughness (ξ) of the coating exist, i.e. with 0.86≤α≤0.91 and 0.56≤β≤0.93 for 0.01≤P_s≤1. These values are different from those reported for sequential, pseudo-time lattice simulations on planar surfaces, signifying the importance of multiparticle dynamics and surface curvature. The internal structure and porosity of the coating are characterized quantitatively by the radial density profile, pair correlation function, two-point probability function, void distribution function and pore area distribution. For RLD the radial density, ρ_n, remains nearly constant, while for DLD ρ_n follows a power law, . The coating exhibits short ranged order in the RLD regime while a long range order is created by DLD. The void distribution function becomes broader with increasing P_s, indicating that in the RLD regime the coating consists of small and spherical pores, while in the DLD regime large and elongated pores are obtained. The pore area distribution shows narrower distributions in DLD for small pores, while the area of the largest pore increases by nearly three orders of magnitude as one moves from the RLD to the DLD regime. Such morphological diversity could be potentially exploited for applications such as percolation, catalysis and surface protection.